Nicki, I'm not sure about the implications for donor, but I asked the nurse at the clinic this very question last week. She said that after our treatment was completed and presuming we were succesful, or had decided not to continue with IVF, then we could donate our embryos if we wanted to. It is not something they would do while we were still trying to conceive though. And I think it has to be done within 5 years of retreival.
I was actually interested in egg donation, but you have to be under 35, so I'm already past it.
I shouldn't imagine the implications would be too grave with donor, as the donor has already given consent. Why not give your clinic a ring in the morning. I'm sure they'll be able to give you a proper answer.

I am not certain where you are located...but there is a group called snowflakes embryo donation that I've heard about - and may use later. I think there are several groups out there...I am just starting to look and won't make any decisions until I am ready to donate; right now we are at week 12 of our pregnancy so have a ways to go.

Our egg donor gave up all rights at the time of donation, so we have to make all the decisions for our embryos. Not sure about your agreement with your donor!